DETECTING MEDIA WATERMARKS IN MAGNETIC FIELD DATA

• US 20140343703A1
• Filed: 12/18/2013
• Published: 11/20/2014
• Est. Priority Date: 05/20/2013
• Status: Active Grant

• Current Assignee: The Nielsen Company LLC (MOOD Media Corporation)
• Original Assignee: The Nielsen Company LLC (MOOD Media Corporation)
• Inventors: Topchy, Alexander, Srinivasan, Venugopal
• Granted Patent: US 9,679,053 B2
• Time in Patent Office: Days
• US Class Current: 700/94
• CPC Class Codes: G06F 16/683 using metadata automatically derived from the content
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00

Abstract

Methods, apparatus, systems and articles of manufacture (e.g., physical storage media) to detect media watermarks in magnetic field data are disclosed herein. Example methods disclosed herein to detect media watermarks can include accessing multidimensional magnetic field data representative of values of a magnetic field measured within a first distance of audio circuitry that is to output an audio signal corresponding to media presented by a media device. Such example methods can also include processing the multidimensional magnetic field data to detect a watermark included in the audio signal.

Claims

1. A method to detect media watermarks, the method comprising:

accessing multidimensional magnetic field data representative of values of a magnetic field measured within a first distance of audio circuitry that is to output an audio signal corresponding to media presented by a media device; and

processing the multidimensional magnetic field data to detect a watermark included in the audio signal.

2. A method as defined in claim 1, wherein accessing the multidimensional magnetic field data comprises obtaining the multidimensional magnetic field data from an interface providing access to a magnetometer of a portable device.

3. A method as defined in claim 1, wherein the multidimensional magnetic field data includes a plurality of directional components, and processing the multidimensional magnetic field data comprises:

processing the directional components to determine magnitude values representative of a magnitude of the magnetic field over time; and

processing the magnitude values to detect the watermark included in the audio signal.

4. A method as defined in claim 3, wherein processing the magnitude values comprises:

transforming the magnitude values into a frequency domain to determine transformed magnetic field data; and

processing the transformed magnetic field data to detect the watermark.

5. A method as defined in claim 4, wherein the watermark modulates a first frequency of the audio signal, accessing the multidimensional magnetic field data comprises accessing the multidimensional magnetic field data at a first sampling rate less than twice the first frequency, and processing the transformed magnetic field data comprises evaluating the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by accessing the multidimensional magnetic field data at the first sampling rate.

6. A method as defined in claim 4, wherein the audio circuitry drives a speaker that is to emit the audio signal, the watermark is included in a first frequency range of the audio signal, the first frequency range being below a threshold of frequencies capable of being emitted by the speaker, and processing the transformed magnetic field data comprises evaluating a portion of the transformed magnetic field data corresponding to the first frequency range to detect the watermark.

7. A method as defined in claim 3, wherein the multidimensional magnetic field data is first magnetic field data, and processing the magnitude values comprises:

correlating the magnitude values with a reference sequence to determine second magnetic field data; and

processing the second magnetic field data to detect the watermark.

8. A method as defined in claim 1, wherein the audio circuitry comprises speaker leads electrically coupling a speaker to a speaker driver circuit, and processing the multidimensional magnetic field data comprises detecting variations in the magnetic field that are induced by an electrical signal being carried by the speaker leads to cause the speaker to output the audio signal.

9. A tangible machine readable storage medium comprising machine readable instructions which, when executed, cause a machine to at least:

access multidimensional magnetic field data representative of values of a magnetic field measured within a first distance of audio circuitry that is to output an audio signal corresponding to media presented by a media device; and

process the multidimensional magnetic field data to detect a watermark included in the audio signal.

10. A storage medium as defined in claim 9, wherein the multidimensional magnetic field data includes a plurality of directional components, and the machine readable instructions, when executed, further cause the machine to:

process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time;

transform the magnitude values into a frequency domain to determine transformed magnetic field data; and

process the transformed magnetic field data to detect the watermark.

11. A storage medium as defined in claim 10, wherein the watermark modulates a first frequency of the audio signal, and the machine readable instructions, when executed, further cause the machine to:

access the multidimensional magnetic field data at a first sampling rate less than twice the first frequency; and

evaluate the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by accessing the multidimensional magnetic field data at the first sampling rate.

12. A storage medium as defined in claim 10, wherein the audio circuitry drives a speaker that is to emit the audio signal, the watermark is included in a first frequency range of the audio signal, the first frequency range being below a threshold of frequencies capable of being emitted by the speaker, and the machine readable instructions, when executed, further cause the machine to evaluate a portion of the transformed magnetic field data corresponding to the first frequency range to detect the watermark.

13. A storage medium as defined in claim 9, wherein the multidimensional magnetic field data includes a plurality of directional components, and the machine readable instructions, when executed, further cause the machine to:

process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time;

correlate the magnitude values with a reference sequence to determine second magnetic field data; and

process the second magnetic field data to detect the watermark.

14. An apparatus to detect media watermarks, the apparatus comprising:

a magnetic field estimator to access multidimensional magnetic field data representative of values of a magnetic field measured within a first distance of audio circuitry that is to output an audio signal corresponding to media presented by a media device; and

a watermark detector to process the multidimensional magnetic field data to detect a watermark included in the audio signal.

15. An apparatus as defined in claim 14, wherein the apparatus at least one of includes or is able to communicate with a magnetometer, and the magnetometer is to provide the multidimensional magnetic field data.

16. An apparatus as defined in claim 14, wherein the multidimensional magnetic field data includes a plurality of directional components, the magnetic field estimator is to process the directional components to determine magnitude values representative of a magnitude of the magnetic field over time, and the watermark detector is to process the magnitude values to detect the watermark included in the audio signal.

17. An apparatus as defined in claim 16, wherein the watermark detector comprises:

a frequency transformer to transform the magnitude values into a frequency domain to determine transformed magnetic field data; and

a watermark decoder to process the transformed magnetic field data to detect the watermark.

18. An apparatus as defined in claim 17, wherein the watermark modulates a first frequency of the audio signal, the magnetic field estimator is to access the multidimensional magnetic field data at a first sampling rate less than twice the first frequency, and the watermark decoder is to evaluate the transformed magnetic field data at a second frequency different from the first frequency to detect the watermark, the second frequency selected to compensate for aliasing caused by the multidimensional magnetic field data being accessed at the first sampling rate.

19. An apparatus as defined in claim 17, wherein the audio circuitry drives a speaker that is to emit the audio signal, the watermark is included in a first frequency range of the audio signal, the first frequency range being below a threshold of frequencies capable of being emitted by the speaker, and the watermark decoder is to evaluate a portion of the transformed magnetic field data corresponding to the first frequency range to detect the watermark.

20. An apparatus as defined in claim 16, wherein the multidimensional magnetic field data is first magnetic field data, and the watermark detector comprises:

a correlator to correlate the magnitude values with a reference sequence to determine second magnetic field data; and

a watermark decoder to process the second magnetic field data to detect the watermark.